Topographic
Relationships Contours and Normal Constrictions of Esophagus
The esophagus begins in the neck as
a continuation of the pharynx (cervical esophagus). This point of origin
corresponds to the inferior border of the cricoid cartilage and the
lower margin of the inferior pharyngeal constrictor muscle, also called
the cricopharyngeus muscle, at about the level of the sixth cervical
vertebra. The esophagus extends inferiorly through the neck and through the
superior and posterior mediastina of the thorax. It then passes through the
esophageal hiatus of the diaphragm to join the cardiac region of the
stomach at about the level of the 10th thoracic vertebra.
The esophagus generally follows the
anteroposterior curvature of the vertebral column, except in the inferior
portion, which is tethered by its relationship with the diaphragm. It also
forms two lateral curvatures, so that in a coronal view, it assumes the form of
a gentle reversed “S.” The upper of the two lateral curvatures is convex toward
the left, and the lower curvature, in the lower thorax and abdomen, is convex toward
the right. From its commencement at the lower margin of the cricoid cartilage,
the esophagus inclines slightly to the left until its left border projects
approximately onefourth inch to the left of the tracheal margin. It then
swings somewhat to the right, reaching the midline at about the level of the
fourth thoracic vertebra behind the aortic arch. It continues its inclination
to the right until about the level of the seventh thoracic vertebra, where it
again turns left somewhat more sharply than in its previous curves, and in this
direction it passes through the esophageal hiatus.
The esophagus has cervical,
thoracic, and abdominal portions. Anterior to the cervical portion lies the
membranous posterior wall of the trachea, to which it is rather loosely
connected by loose connective tissue and some smooth muscular strands, so that
the anterior esophageal and the posterior tracheal walls are occasionally
referred to as the “common party wall.” In the grooves on each side between the
trachea and the esophagus are the recurrent laryngeal nerves, which
ascend from the vagus nerves in the upper thorax to reach the larynx.
Posteriorly, the esophagus lies upon the prevertebral fascia, covering the
anterior surface of the longus colli muscles and cervical vertebral
bodies. On the left and right, the carotid sheath and the structures it
contains (vagus nerve, carotid arteries, and internal jugular vein) accompany
the cervical esophagus. Owing to the curvature of the esophagus in this region,
it lies closest to the left carotid sheath. The lobes of the thyroid gland partially
overlap the esophagus on each side. The thoracic duct ascends in the
root of the neck on the left side of the esophagus and then arches laterally
posterior to the carotid sheath and anterior to the vertebral artery and
vein to enter the left brachiocephalic or left subclavian vein at
the medial margin of the anterior scalene muscle.
The thoracic esophagus also
lies posterior to the trachea as far as the level of the fifth thoracic
vertebral body, at which point the trachea bifurcates. The trachea deviates
slightly to the right at its lower end, so that the left main bronchus crosses
anterior to the esophagus. Below this point the esophagus is separated
anteriorly from the left atrium of the heart by the pericardium. In the very
lowest portion of its thoracic course, the esophagus passes posterior to the
central tendon of the diaphragm to reach the esophageal hiatus. On the left
side in the superior thoracic region, the esophageal wall contacts the
ascending portion of the left subclavian artery and the parietal pleura; at
about the level of the fourth thoracic vertebra, the arch of the aorta passes
posteriorly alongside the esophagus. Below this point the descending
aorta lies to the left, but when it passes posterior to the esophagus, the
left mediastinal pleura again comes to abut on the esophageal wall. On the
right side the right parietal pleura is intimately applied to the
esophagus, except when, at about the level of the fourth thoracic vertebra, the
azygos vein intervenes as it turns anteriorly. The short abdominal portion of
the esophagus lies upon the diaphragm and ma es an impression on the liver
with its anterior aspect.
The left and right vagus nerves
associate with the esophagus, and below the tracheal bifurcation, they
interweave to form the esophageal plexus of nerves. This plexus then
coalesces with the anterior and posterior vagal trunks that
pierce the diaphragm along the esophagus.
The course of the esophagus is
marked by several indentations and constrictions:
1. The first narrowing of the esophagus is found
at its commencement, caused by the cricopharyngeus muscle at the inferior
border of the inferior pharyngeal constrictor and the cricoid cartilage.
2. The esophagus is indented on its left side by
the arch of the aorta (aortic constriction), and at this level the
aortic pulsations may often be observed through the esophagoscope.
3. Just inferior to this point the left main
bronchus causes an impression on the left anterior aspect of the esophagus.
4. At its lower end the esophagus is narrowed by
the diaphragmatic constriction (inferior esophageal sphincter) as it
passes through the right diaphragmatic crus.
The overall length of the esophagus
varies in accordance with the length of the trunk of the individual. The
average distance of the cardia from the upper incisor teeth is approximately 40
cm, but in some “long” individuals this distance may be as much as 42 or 43 cm.
This average distance of 40 cm may be sub divided as follows: The distance
from the incisor teeth to the cricopharyngeus muscle, which corresponds to the
commencement of the esophagus, averages 16 cm. It is thus apparent that the
average length of the esophagus itself is 40 minus 16 cm equals 24 cm, or
approximately 10 inches. At about 23 cm from the incisor teeth, the arch of the
aorta crosses the esophagus on its left side. This crossing is therefore about
7 cm below the cricopharyngeus. A few centimeters below this point the left
main bronchus passes anterior to the esophagus. The diaphragmatic constriction,
or commencement of the abdominal part of the esophagus, is located at about 37
to 38 cm from the incisor teeth. It is of considerable significance to note
that the esophageal hiatus of the diaphragm is slightly inferior (≈ 1 cm) to
this point, and the cardiac region of the stomach is at a still slightly lower
level. The figures given above are for adults; in children the dimensions are
proportionately smaller. At birth the distance from the incisor teeth to the
cardiac region is usually only 18 cm, at 3 years approximately 22 cm,
and at 10 years approximately 27 cm.
Although the esophagus is usually
described as tubelike, it is generally flattened so that the transverse axis
is somewhat larger than the anteroposterior axis. In the resting state the
esophageal walls are in approximation. The width or diameter of the esophagus
varies considerably with its state of tonus but the average resting width
is approximately 2 cm.
